With the wind chill well below zero and the sky still black, more than 300 strikers lined the sidewalks this morning outside Geo. A. Hormel & Co. and watched 800 National Guardsmen escort their permanent replacements into the plant.

"There is going to be blood here," said Jerry Simes, 44, whose savings have been depleted by the five-month strike. "There may not be blood here today, but they can't keep the National Guard here forever . . . and these scabs are taking our jobs."

This usually peaceful company town has been torn apart by one of the longest and most militant strikes in recent years. The bitter crusade has drawn national attention because of the local union's unusually strong resistance to concession demands from a prominent corporation that had long since settled with locals elsewhere.

Gov. Rudy Perpich ordered out the Minnesota Army and Air National Guard on Monday -- and reinforcements Tuesday -- at the request of town officials who feared violence. The 1,500-member meatcutters' union had twice blocked access to the plant after Hormel announced its intention to reopen with replacements and union members willing to return.

In this economically depressed Farm Belt region of southern Minnesota, more than 3,000 applicants were willing to take the $8-an-hour Hormel jobs. About 50 to 100 workers entered the plant about 6 a.m. today after police and guardsmen sealed off the I-90 exit ramp leading to the Hormel grounds and reserved it for strike replacements.

"We are under siege in this town, and we feel it is perfectly appropriate for the National Guard to be here," Hormel Vice President Charles Nyberg said.

"The National Guard is now being used as Hormel's private security force," said James Guyette, president of Local P9 of the United Food and Commercial Workers Union. "Taxpayers should not be paying for a security force to run scabs into the plant."

Austin has been the home of Hormel since 1891. Mayor Thomas Kough, a 31-year Hormel engineer, is on strike, but two of the seven city aldermen are crossing the picket line to their jobs.

"This is tearing us up," said Mower County Sheriff Wayne Goodnature, whose voice cracked with emotion as he told reporters about his decision to ask for the Guard. "I have friends on both sides of this, and I can't describe to you how this is tearing me up."

The unrest began 15 months ago when Hormel, despite consistent annual profits of $25 million on sales of Spam, Dinty Moore stew and other popular products, announced a 23 percent cut in hourly wages, from $10.69 to $8.25. The company said competitors in the depressed meatpacking industry had already cut wages, and arbitrators upheld the company's contractual right to do so.

While unions at six other Hormel plants agreed to concessions and negotiated new contracts, Austin workers insisted that they had already made substantial concessions and that Hormel's record profit on sales of $1.5 billion for 1985 made concessions unnecessary.

"We helped pay to build this new building . . . . We took payroll deductions to build it. And now they've got me locked out of it," said Larry Gullickson, 41, a "hog sticker" whose job was slaughtering 900 pigs per hour. Austin workers gave up an average of $12,000 each in bonus pay in recent years to help Hormel open the new plant in 1982.

Opposition grew with disclosures that chief executive Richard L. Knowlton had received a $230,000 pay increase, bringing his salary to more than $550,000, and had raised other executives' pay an average of 19 percent.

After months of negotiations, Hormel made a final offer last August of $10 an hour, a three-year wage freeze, a pay cut for newly hired workers, and weakened seniority and work rules, a package already overwhelmingly rejected by the union.

P9 prepared for war. Its members hired a New York labor consultant, Ray Rogers, who coordinated an anti-Hormel campaign that has included extensive boycott and picketing efforts, nationwide fund-raising and emergency food and clothing programs for strikers. About 200 unions around the country participated in an "Adopt a P9 Family" drive to help strikers pay their bills.

The strikers are union members whose fathers and grandfathers organized here in 1933, waging the first recorded sit-down strike in the United States. The local union has returned to its militant tradition in a manner described by its international president, William Wynn, as "mass suicide." Austin workers are taking on the company without the endorsement or support of the Washington-based UFCW.

"We have offered them the best contract in this industry, but it is still not enough" to please the union, Hormel's Nyberg said. "We have decided over the course of two years that we have gone as far as we could go . . . . We hope our employes will return to work."

The company would not disclose the number of workers who took jobs today, but the union is gambling that it can hinder production enough to force Hormel back to the bargaining table.

Perpich said union leader Guyette and Hormel president Knowlton agreed to meet Thursday with a neutral fact-finder about the dispute. A similar invitation by Perpich two weeks ago failed to bring the sides to negotiations.

"We have lasted five months, and we are going to last until it's finished," said Douglas Snater, 33, a ham-boner who, like others, has been getting by on $40 a week in union strike benefits. "This company is watching people lose their homes over this, people who can't make their payments, but we're not quitting."

"Are we committing suicide? You know, I am not really sure," said Jerry Simes. "Only time will tell."